It is often desirable to seal the opening of a bottle, jar or other container opening using a sealing member to maintain freshness and/or to indicate whether the container has been tampered with. The sealing member often includes a tab to help a consumer remove the sealing member from the container. In use, a user seeking to gain access to the contents of the container simply grips the tab with their fingers and, by pulling on the tab, can remove the sealing member and access the contents of the container in a relatively convenient manner. One example of such a sealing member is described in U.S. Pat. No. 6,866,926. Such sealing members have a hinged tab positioned above a lower seal laminate. The lower seal laminate of these prior sealing members generally includes a heat sealable layer for bonding to the container rim, a metal foil layer for generating heat, and a foam insulation layer above and abutting the foil layer for retaining heat in the lower portion of the seal for activating the heat seal layer.
The foam insulation layer is advantageous in the lower seal laminate under the tab because, with its close proximity to the foil, it helps insulate and protect the upper layers and tab from damage or melting due to the heat experienced by the seal during heat sealing. In particular, the foam helps protect a bonding layer that secures the tab to the lower seal laminate. Often, the bonding layer has a lower melt point that renders it susceptible to melting during field use when an end user applies heat to secure the seal to a container. If the bonding layer melts, it can ooze or flow out of the seal and cause a free end of the hinge-type tab to be bonded to the lower seal laminate. This is called tab-grab and is undesirable. End users, in some cases, will often overheat the seal to make sure that a good heat seal is formed. The foam insulation under the bonding layer helps protect this bonding layer from any overheating. The foam insulation layer in prior seals also helps keep heat in the lower layers of the seal to achieve a uniform heat seal to the container rim between the tabbed and non-tabbed sides of the seal.
Sealing members constructed in this manner, however, generally do not allow for a tamper indicating capability where a portion of the lower seal laminate tears upon a user applying a removal force to the tab. Using the foam insulation layer in the lower seal laminate with a sufficient thickness to impart the insulation and heat retention capabilities for heat sealing generally does not allow for easy tearing of the lower seal laminate portions upon seal removal. The thickness of the foam needed to achieve insulation and heat retention results in a laminate that has relatively high internal tear strength. With these prior insulated and tabbed sealing members, therefore, upon a user pulling on the tab, such sealing members separate in one piece from the container generally without leaving any substantial portions thereof across the mouth of the container opening for tamper evidence.
For such tabbed sealing members to properly effect removal thereof from a container via use of the tab, the structure forming the tab generally needs to remain bonded to the lower seal laminate and the tab needs to remain in one piece. Thus, proper functioning of these tabbed seals are generally dependent on the tear strength of the layers forming the tab as well as the bond strength of the tab to the lower seal laminate. Historically, alterations of tab materials or down gauging (i.e., making thinner) the thickness of the various layers forming the tab or the adhesive bonding the tab to the lower seal laminate results in undesired tab separation or tearing upon a removal force being applied to the tab. Tearing of the tab or separation of the tab from the lower seal laminate is undesired because it does not properly result in seal removal.